Essential Trace Elements Required by Humans
The nine known essential trace elements required by humans are chromium, copper, fluorine, iodine, iron, manganese, molybdenum, selenium, and zinc. 1
The Nine Essential Trace Elements
According to ESPEN (European Society for Clinical Nutrition and Metabolism) guidelines, these trace elements are definitively classified as essential for human health and survival 1:
- Chromium - Required in doses of 10-15 mcg/day 1
- Copper - Required in doses of 0.3-0.5 mg/day (4.7-7.9 mmol) 1
- Fluorine - Essential trace element 1
- Iodine - Required in doses of 70-130 mcg/day 1
- Iron - Essential for oxygen transport and enzyme function 1
- Manganese - Required in doses of 60-100 mcg/day (1.1-1.8 mmol) 1
- Molybdenum - Required in doses of 10-25 mcg/day 1
- Selenium - Required in doses of 60-100 mcg/day (0.8-1.3 mmol) 1
- Zinc - Required in doses of 2.5-4 mg/day (38-61 mmol) 1
Additional Trace Elements Under Investigation
Beyond the nine definitively essential elements, research suggests cobalt may also be essential (primarily as a component of vitamin B12), though its independent essentiality remains under investigation 2, 3. Some sources list 11 essential trace elements by including cobalt 2, while others identify up to 19 potential essential trace elements as research continues 2.
Nickel, boron, and vanadium are considered "probably essential" but lack definitive proof of essentiality in humans 4, 3.
Clinical Significance and Monitoring
Regular monitoring of trace element status is critical in high-risk populations, particularly those on parenteral nutrition, as deficiencies develop rapidly but clinical manifestations may take weeks to appear 1. Biochemical alterations occur within 3-5 days, while biological deficiency syndromes occur even earlier 1.
Key monitoring recommendations:
- Baseline measurements should be obtained at the onset of home parenteral nutrition (HPN) 1
- Annual monitoring is recommended for stable patients on long-term parenteral nutrition 1, 5
- Monthly monitoring is indicated for critically ill or hypermetabolic patients on prolonged parenteral nutrition, with particular attention to selenium and zinc deficiency 1, 6
Common Pitfalls
The major clinical challenge is that good markers of overall trace element status are available only for a limited number of these elements, and few clinical laboratories are equipped to measure them 1. This creates difficulties in identifying deficits early and monitoring supplementation effectiveness 1.
Deficiency and toxicity are both dose-dependent, and the early pathological manifestations are difficult to detect until more specific indicators become available 4. For example, selenium deficiency worsens oxidative stress in critically ill patients and can cause endemic cardiomyopathy 1, 2, while zinc deficiency causes telogen effluvium and brittle hair in patients on prolonged parenteral nutrition 6.